Metal plate dimpling machine



Dec. 11, 1945. L. c. HucK METAL PLATE DIMPLING MACHINE Original Filed Aug. ll2, 1,940 2 Sheets-Sheet l Dec. l1, 1945. L. c. HUCK 2,390,5375

METAL PLATE DIMPLING MACHINE I original' Filed Aug. 12, I1940 z sheets-sheet 2 'jvais-. )fa el. 1

Patented Dec. 11, 1945 2.390.531 mar. rL'ra Dramma MAcmNn Louis C. Huck. Grosse Pointe Shores, Mich., asor, by meme assignments, to Hnxon Holding Corporation, Detroit, Mich., a corporation of Michigan v Original application Amst 12, 1940, Serial No.

8 Claims.

The invention relates generally to riveting and Y it has particular relation to dimple riveting and the formation of dimples in metal sheets to be tionv for patent, especially in conjunction with aircraft, it is extremely desirable in the riveting of the metal skin or cover, to employ rivets having heads ilush with the surface of the cover in lorder to eliminate projections on surfaces exposed to air ow. It is a general practice in such cases where the metal cover is too thin to allow counter-sinking, to dimple the metal around each rivet hole so as to provide a recess for the rivet head. Dimpling of the metal is particularly advantageous, in that it increases the shear strength of the riveted joint, since the contacting dimpled portions of the overlapping metal sheets provide a means, `in addition to rivet, for carrying the'shear load.

An lobject of the invention is to provide an eillcient, small, and easily maneuverable dimpling apparatus, which is operated by iluid pressure.

Another object of the invention is to provide dimpling apparatus such as mentioned heretofore, which includes. means for centering and guiding a mandrel into the end .of a dimpling tool forming part of the apparatus.

Another object of the invention is to provide a mandrel centering and guiding device such as last mentioned which automatically is retracted to an out of the way position during the dimpling operation so that it will not interfere withmovement of the tool into engagement with the sheet metal.

Another object of the invention is to provide improved means for `modifying the tendency of the sheets to bend `during the dimpllng operation Divided ma 194s, serial No. m

this application May 19, ,582

of dimple riveting. As discussed in that applica? so that bending will be avoided or controlled in a desirable manner. v

Another object of the invention is to provide an improved dimpling apparatus having means for counteracting thistendency of the sheets to bend during the bending operation, wherein the action of this counteracting means may be varied by adjustments provided for this purpose.

Another object of the invention is to provide an improved dimpling apparatusA for dililpllngl assembled metal sheets which includes mandrel or pin gripping jaws and a means for automatically retracting or releasing the jaws at the end of the dimpling operation, so that the mandrel or pin may be easily released and again inserted.

Another object of the invention is to provide an improved method of dimpling metal sheets which will require minimum forces while still allowing a suitable dimple to be formed without breaking or cracking of the dimpled metal.

Another object of the invention is toprovlde an improved mechanism for dimplins metal sheets which will enable forming the dimple with minimum forces and which will automatically govern the formation of the dimple'y by controlling the amount of force applied.

Another object of the invention is to provide an improved mechanism for dimpling metal sheets wherein the dimpling operation will automatically be governed by stop means limiting the relative movement;` of.: the dimpling members.

Other objects of the invention will become apparent from the following description, from the drawings forming a part of the speciilcation, and from the claims hereinafter set forth.

For a better understanding of the invention, reference may be had to the drawings. wherein:

Figure l is a longitudinal view, mainly in longitudinal section, of apparatus for forming dimples in assembled metal sheets, as constructed according to one form of the invention;

Fig. 2 is a cross-sectional view taken substantially along the line 2-2 of Fig. 1; Fig. 3 is a sectional view taken substantially along the line 3-3 of Fig. 2; and

Fig. 4 is a fragmentary view on the order of Fig. 1, illustrating the relation of parts approximately at the end of the dimpling operation.

Referring to Fig. 1, the dimpling mechanism or gun as shown comprises a cylinder I9 4having a handle Il secured thereto by suitable means not shown, so that the gun may be manually held and manipulated. The cylinder I Il has an inner cylindrical wa1l |2 slidably receiving a piston VI3 having suitable sealing rings I4 for preventing a leakage of fluid between the wall and piston. At its right hand end, the cylinderis closed by an integral wall portion, exceptlng'for a uid passage l5, and this passage leads to an annular passage I1 at the junction of the handle and cylinder and in turn the annular passage I1 communicates with a passage Il extending through the handlefor connection with a uid conducting. line I9. p v

At its left end the cylinder I0 is enlarged thereby forming a shoulder 22 and within the enlargement a bushing 23 is threaded as indic'ated at 24. Anfannular end member 25 has a cylindrical portion 28 slidably receiving a piston rod 21 projecting from the piston I3 and a recess 28 having packing rings 29 engaging the rod and this member is held in place at the left of the cylinder by a collar 30 thereon disposed between the end of the bushing 23 and the shoulder 22. A gasket 3| is located between the shoulder and collar 22 to prevent leakage of iluid at this point.

The extreme right end of the member 25 has an annular relief 35 which communicates with a fluid passage 31 extending laterally through the wall of cylinder I and communicating with a passage 38 leading to the handle The passage 38 also extends through a projection 4| on the cylinder I0 disposed in a similar opening 42 in the handle and from this point the passage is connected with a passage 43 leading to an outlet 44. Sealing gaskes 45 and 48 disposed at the junction of the casing and handle portions prevent leakage of iiuid,

The piston rod 21, at its left end, terminates in a threaded portion 50 Aand on this threaded portion a jaw holder 5| is threaded and is retained in place by means of a lock nut 52. The left end of the jaw holder is provided with a plurality of circumferentially arranged sockets 53, which converge toward the left end of the jaw holder and which respectively receive similarly shaped jaws 54. The sockets and surfaces of the jawsVmay represent conical forms, or, in other words, the surface of each socketand the outer surface of each jaw may form a section of a conical surface, -with the surfaces having substantially full surface contact when the jaws are in clamping positions. Grooves 56 in the inner faces of the jaws are adapted to engage a grooved mandrel to be mentioned presently, and when the end of the mandrel is between the jaws, movement of the jaw holder to the right will cause the jaws to grip the mandrel.

The jaws are urged towards the left end of the jaw holder by means of a jaw follower 51 mounted on a reduced end portion 58 of a plunger 59 that is slidably mounted in a bore 68 in the left end of the piston rod. A spring 6| in such bore urges the plunger 59 and jaw follower 51 to the left and hence the jaws to the left end of the jaw holder. It may be observed that the right ends of the jaws have angled or tapered faces 64 and that the left end of the follower 51 is similarly tapered as indicated at 65, and this relation of surfaces is provided in order to eect expansion of the jaws when forced to the right relatively to the jaw holder.

The bushing 23 has an outer cylindrical portion 61 threaded as indicated at 68 and upon which a barrel 69 is threaded, and the latter at its left end has an inwardly extending end wall 'III terminating in va threaded aperture cent the end of the jaw holder l. A`metal dimpling tool 12 is threaded into the threaded aperture 1| until a head 13 thereon engages the wall of the barrel and the inner end of the tool is shaped to ilt the left end of the jaws so as to provide an abutment which serves to force the jaws rearwardly when the jaw holder and piston move to the left. In other words, just before the piston reaches its left limited position, the jaws strike the end of the tool 12 and are moved to the right relative to the jaw holder 5| and also radially outwardly into releasing position due to the v relation of the surfaces 84 and 85 on the jaws and follower 51. Hence, the jaws move outwardly in their sockets to releasing positions and this movement is such that the mandrel mentioned previously-may be freely removed axiallyA from the jaws. AIt may be observed lhere that thetool 12 has 'an axial bore 15 leading to the jaws so that the mandrel may be inserted axially through the tool and into position between the jaws.

For dimpling sheets of metal indicated at 11 and 18 disposed in overlapping relation, a die 19 is employed which has a recess 88 into which the metal is forced during the dimpling operation and a'rounded edge 8| adapted to-engage the sheet -metal around the dimpling area for supporting the metal.' This die is centrally apertured as indicated at 82 and the mandrel previously mentioned and indicated at 84 extends through this opening. The mandrel may have a press t in the opening 82 so that it will not be easily removable and has a head portion 83 for preventing pulling of the mandrel through the die during the dimpling operation. It may be noted that the die outwardly of the recess 80 has its face next to the sheet metal 11 relieved as indicated at 85 and the purpose of this is to provide a space for the sheet metal to be axially pressed to the left around the dimpling area in counteracting or modifying bending caused by the dimpling operation. The mandrel 84 has a grooved or ribbed end 86 adapted to fit between the grooved jaws 54 in order to positively lock the jaws and mandrel together during the dim'.

pling operation. For forcing the sheet metal intoy the die recess 80, the tool 12 has a frusto conical end 81, which, when moved against the sheet, dimples the sheets into the die recess 88.

vIt is to be observed that the die recess has a at bottom 88 and a cylindrical side wall 89 and that the edge of the sheet metal is flattened against the bottom 88 during the dimpling operation while the metal between the shoulders 8| and the Vflattened edge is unsupported. This flattened edge is indicated at 98 and during its formation the metal is upset along the mandrel as indicated at 99. Flattening of the metal edge prevents splitting or cracking and thereby allows the dimple to be formed without danger of splitting. At the same time, by leaving the metal unsupported between the edge 98 and shoulder 8|, it is easier to form' the dimple and, therefore, a smaller force may be used and this is of considerable importance since smaller pressures may be used that will not endanger breaking of the mandrel 84. It may be observed that the dimple portions tend to extrude or shift towards the die along wall 89 of the latter a slight amount due principally to the fact that the diameter of the wall 89 is less than the diameter of the tool 12 plus the doubled thickness of the sheets 11 and 18.

During dimpling of sheets such as mentioned. I

bending of the latter around the dimpling area tends to occur, and if not counteracted or modified the sheets finally will becomey bowed or arcuate and this may be undesirable; To oiset or modify this tendency of the sheets to bend, means are provided which will be described pres- `76 ently for exerting a force against the sheets dur-` ing the dimpling operation and this force tends to bend the sheets over the rounded edge 8|'o'f the die and towards thek relief in the die?I acci It may be desirable when the dimpling'bperation is effected to have the sheets remain dat, but

, into the opening. formed rapidly, some delay might be incurred in repeatedly inserting a mandrel into the end of be desirable to variably control the of bending of the sheets over the edge so that finally the sheets will have a contour. It would he even-feasible to vary the force lapplied to the sheets to bend -them that the sheets as finally `rlimpled would Itmay be mentioned now that the frustoi conical end oi' the tool 12 presents a problem of mandrel insertion into the bore 10, because the opening for inserting the mandrel is approximately the same size as the mandrel Vand there is nothing on the tool end to guide the mandrel Where dimples Amust be the tool without guiding means and the construction to be described solves this problem.

Again directing attention to Fig. l, it will be observed that inner and outer sleeves 90 and 9| are mounted on the barrel 69 and these sleeves are threadedly connected at 92, so that the sleeves may be moved axially in a relative sense by turning one with respect to the other. `The sleeve 90 is maintained on the barrel by circumferentially separated pins 93 on the barrel which are slidably arranged in slots 94 in the wall of the inner sleeve with the slots having closed ends so that the sleeves 90 cannot normally be removed. The two assembled sleeves are normally urged to the left end of the construction by a coil spring 99 encircling the barrel and engaging a collar 96 at the right end of the latter and a shoulder 91 on the outer sleeve 9|. tention is directed to the fact that the .barrel has a shoulder which is in a position to ensage the shoulder 91 on the sleeve 9| when sufilcient relative movement of the barrel and sleeve occurs in an axial direction. A ilange or rim |0| on the sleeve 9| normally will prevent anyone from accidentally having a iinger caught between the two shoulders during operation of the mechanism and also will prevent external objects of other character from becoming disposed in the space between the two shoulders.

The left end of the sleeve 90 has a relatively thick end wall |which is apertured at its cen- `ter as indicated at |06 for allowing passage of the tool 12 through the wall. Now for providing a means for facilitating the insertion of the end oi' the mandrel into the frusto conical end of the tool 12, radially disposed guide members are provided in the end wall |05 and these members have pin portions |01 slldably mounted in radial openings |00 in such wall. Springs |09 in the open- 'ings |09 urge the members inwardly and the cuter ends oi' the springs are retained in the openings by plugs ||0 suitable secured in the outer end 0i' the latter. The inner ends of the pins |00 carry centering or guiding portions respectively. and these centering portions, when brought together as shown in Figs. 1, 2 and'3. jointly form a frusto conical cavityat the right side which fits the irusto conical end of the tool 12, and at the 'left side, a frusto conical cavity ||2 for guiding the pin 94 into the bore ci tool 12. It is to be observed thatthe portions are disposed in an annular channel shape recess ||3 and that they are guided radially by the walls of the recess. It may be noted also that the centering devices are formed at their'center to provide an opening which will allow the end of the mandrel to bepushed therethrough.

With the sleeve 99 moved to its extreme left position as governed by the slots 9i and pins il, it will be apparent that the spring pressed guiding devices will be urged to the positions shown in Fig. l, so that they will form a centering and guiding cavity which renders it easy to insert the end of the mandrel. On the other hand, it will be apparent that the sleeve can be moved to the right easily and against the action of the spring 90 and the plunger springs- |09 and that during Vthis operation the guiding devices will be moved outwardly by the tool 12, thereby allowing the latter to pass through the end wall |99y of the sleeve.

For applying pressure to the 'sheets iin order Vto modify the bending tendency, a rubber bushe ing I5 is mounted on the end face of the wall |00 and this bushing may be retained in place by an overhanging ilange ||9 although it may be desirable to bond the bushing to the en d tace of the wall. 'lhis rubber sleeve is adaptedto engage the sheet 19 and resiliently to apply pressure thereto during the dimpling operation. A ttention is directed to the i'act that an angular ring |20 confines the inner corner edge of the bushing at its outer end and this washer is provided mainly to prevent the rubber from being deformed inwardly into a position where it would be caught iby the tool moving into the die during the dimpling operation. In other words, it confines the corner at this point and governs the bow of rubber and at the same time a radial leg of the Washer provides a metal face contact with the sheet immediately adjacent the dimpling area and this may be found desirable in order to insure ilatness ci the sheet immediately adjacent the edge of the dimpling area.

It has been stated that the shoulder |00 on the barrel 99 is adapted to engage theshoulder 91 on the sleeve 9|, and that this engagement will occur after a predetermined relative axial movement of the sleeve and barrel In other words, the distances between the two shoulders governs the movement required before engagement. For varying the distance between the two shoulders, it is only necessary to turn the sleeves 90 and 9| relatively which will adjust the position of the shoulder 91 on sleeve 9| with respect to the ends of slots 94 and pins 99, holding the sleeve 90 in'its outermost position. While it is desirable to have the sleeves 90 and 9| relatively turnable in order to make this adjustment, `it is also expedient that turning not accidentally occur and in order to normally prevent turning of sleeve 9| on the sleeve 90, a plunger |'|9 is provided as shown by Figs. 2 and 3. This plungeris disposed in a recess |2| inthe end wall |05 of sleeve 90 and is pressed outwardly by means oi a spring |22. 'I'lie outer end of the -plunger is adapted to selectively fit circumierentially spaced notches |23 arranged -on the inner periphery of the end of sleeve 9| and the outer end of the sleeve overhangs the plunger ||9 so that normally release oi' the plunger will not occur. When it is desired to relatively turn the sleeves, the plunger may be pushed inwardly by any suitable instrument and then the sleeve 9| may be turned on the sleeve 90 until the sleeves are in the positions desired, and then the plunger may be allowed to enter an adjacent notch |20. It will be apparent. of course, that the pins 93 on the barrel 6 9 prevent turning ot the sleeve 90 relatively to the barrel.

Fluid \under pressure may be conducted through the lines I9 and M to either side of the piston I9 and ordinarily high iiuid pressure will be required at the left side of the piston since movement of the piston to the right is the working movement while a lower iluid pressure may be used to return the parts to their original positions, it being understood that fluid will exhaust at one side of the piston while being allowed to flow into the cylinder at the opposite side of the piston.

Assuming that the dimpllng operation is now to be performed, the die 19 with attached pin is associated with the sheets 11 and 18 and the y'mandrel is passed through a previously drilled opening in the sheets around which the dimpling is to occur. The dimpllng mechanism is moved over the projecting mandrel to the position shown in Fig. 1 and .it will now be readily apparent that when the mechanism is moved over the projecting end of the mandrel, the guiding devices III will facilitate movement of the mandrel into the end of the tool 12.

When the parts are positioned as shown in Fig. l', and the rubber bushing is against the sheet 18, the operator applies further pushing effort to the mechanism and toward'the sheet 18 and this will cause the barrel 69 and tool 12 carried thereby to move to the left relative to the sleeves 90 and 9|, and, as a result, the tool- 12 will spread the guiding devices III and move through the end wall and through the rubber bushing. During this action, the spring 95 is compressed and the shoulders 91 and |00 relatively approach each other. Final movement of the 'plunger 12 manually in this respect, causes the grooved end of the mandrel to move into the space between the jaws 54 until it engages the endv of/the reduced portion 58 of the plunger 59. This serves notice to the operator that the parts are in operative position and in particular that the end of the mandrel is located properly between the jaws.

When the parts are in this relation, the fluid under pressure is caused to enter the cylinder at the left side of the piston I3V and to exhaust from the right side of the piston and as a result the piston I3 will move to the right relative to the cylinder. The rst part of this movement will cause the jaw holder 5| to move relative to the jaws 54 and clamping of the jaws about the end of the mandrel will occur. Further movement of the jaw holder and piston then will carry the jaws and mandrel therewith but if the sheets 11 and 18 are in relatively fixed position, the piston l and parts carried thereby instead of moving, will remain stationary so to speak, while the barrel` will move to the left. In any event, after the piston has movedr suillciently to cause the jaws to be clamped about the end of the mandrel, rela- -tive axial movement of the barrel and tool 12 with respect to the mandrel will occur and this will cause the frusto conical end of the tool to move through the bushing and to press the sheets 11 and 18 into the die recess 80 thus performing the dimpling operation. During the dimpling operation, the shoulders |00 and 91 on the barrel 69 and sleeve 9|, respectively will engage each other and then the sleeves 90 and 9| will be directly and positively moved by the barrel and will forcefully press the rubber bushing to apply the 'pressure against the sheet 18. Thus, this pressure becomes positive and direct except for pressure through the rubber bushing and against the sheets 11 and 18. While preliminary movement of the barrel relative to sleeve 9| will compress the spring 95, ordinarily this pressure would not be of such character as to bend the sheets as the spring ordinarily is used to return the sleeves and 9| totheir lefthand position when i the parts return to inoperative positions as seen in Fig. l. By placing the shoulders 91 and I00= closer together, positive and direct pressure to the rubber bushing can be secured earlier and it follows that the pressure applied by the rubber will become greater and greater as the tool and die move together. The amount of pressure thus can be determined by adjustment of the shoulders 91 and |00 relatively, and as stated before, modication of the bending of the sheets during the dimpling operation can be varied and the contour of the sheet can actually be governed as may be found most desirable.

Fig. 4 shows the parts on a larger scale approximately at the end of the dimpling operation. Deformation of the rubber naturally will occur owing to its incompressible character and. accordingly it will expand as shown.

In effecting the aforesaid dimpling operation, a fluid pressure system may be employed as diagrammatically illustrated in Fig. 1 and which generally may correspond to the system embodied in my Patents Nos. 2,088,859 and 2,132,112. This system includes a iiuid tank or reservoir |24, a motor driven pump |25, a control valve |26, -solenoids |21 and |28 for moving the valvesv in opposite directions, respectively, and a pressure booster |29 including a small barrel |3I. The supply line leading from the pump is indicated at |32 and an adjustable relief by-pass valve |38 in this line' is also connected to a return line |84 leading to the tank. The valve allows the liquid to by-pass to the tank when necessary and may be so adjusted that the necessary dimpling pressures in any case will be available before by-passing occurs. Fluid is delivered to the booster when the valve |26 is in one position and from the booster barrel I3I, the fluid flows through a line |36 leading to the valve |26. |26 in one axial position, fluid is supplied to line |9 directly from the pump in order to return' the piston I3 to its inoperative position, whereas, when the valve is reversed, the line 44 is placed in communication with the barrel |3|. Higher pressure is available therefore for the working stroke but when this pressure reaches a denite amount, the valve |33 will allow by-passing from which it follows a definite but adjustably limited pressure may be employed for governing the character of the dimpling action.

A trigger |30 on the handle Il may control switches not shown for either energizing one or the other of the solenoids |21 and |28 depending upon whether the trigger is moved in one direction or the other.

From the foregoing it will be understood that when the trigger is operated to effect the dimthe bottom Il of the die and Athen continued movement of the tool will deepen the dimple since the metal is unsupported between the bot, tom Il and shoulder lLof the die, but the resistance to dimpling increases with the dimpling, and as iiattening of the edge occurs and at a predetermined pressure, the valve |13 will operate to by-pass the liquid to the tank. It should be appreciated that a high pressure is not required to dimple the metal and to get the correct dimple angle sincethe die is unsupporting to the side of the dimple, while at the same time it should be appreciated that cracking is prevented by the iiattening and upsetting oi' the edge of the sheet metal.

Under certain circumstances. liquid under pressure may be supplied tothe line M and air under pressure to the line I9 in accordanceV with the supply system disclosed in my Patent No.

2,053,718, relating to riveting mechanism. In-

this case, the trigger |30 will operate a valve on the handle for connecting and disconnecting the passage Il and line Il to exhaust or atmosphere and operation of the trigger in this way as disclosed in such patent will cause the required movements of the piston.

Upon completion of the dimpling operation, release of the trigger |30 causes the line 4I to become open to return or exhaust while the line Il is open to iluid pressure. Then the piston i3 returns to its lefthand position and ilnally the jaws M strike the right end of the tool 'l2 and that thedie' 19, tool 12, pin anvil Ill, and lother parts will be formed of suitably hard metal this event they may be constructed of an alumi num alloy. It will be understood pursuant to this to perform the functions necessary in the use of the mechanism.

It will be apparent that all of the operations in so far as the use of force is involved occur at only oneA side of the sheets and thatno backing` element requiring forceful manuall holding at the.

opposite side of the sheet is required. In other words, itis only necessary for the operator to insert the mandrel at one side of the sheet and move the. die 19 thereon into position and then it is a simple matter to hold them in that position while the mechanism is moved over the mandrel at the other side of the sheet.

' here that after the dimpling operation, the openexpand so' that the mandrel is released. Then the mechanism can be bodily moved away from the metal sheets following which'the parts may be associated with another opening in order to effect another dimpling operation.

A uid supplying system such as shown in the patent to Peterson, et al., No. 2,163,627 also may be employed in which case the lines I5 and I6 of such patent will correspond with the lines 44 and Il respectively, herein. Also, the switch Il, BI in the`patent will correspond to the trigger |35 in the present application so that operation of the trigger |30 will control the system in the manner that the switch in the patent controls the supplying of fluid under pressurein the lines Il and I8. In using a system of this character. operation of the switch will cause fluid under pressure to be supplied to line 44 until resistance is encountered such as when the end of the tool 12 rst engages the plate 'Il and then a higher ing through the sheets may be enlarged slightly by a drill for example, to provide'a more fully cylindrical and smooth hole, as disclosed in my Patent 2,292,446.

If tne cumphng point is substantially removed from the edges of the sheet, a handle may be employed for allowing the operator to insert the mandrel at a point substantially removed from the edge. A handle |10 is shown on the die for this purpose, although it is to be understood that .the handle may be releasable so that it could be connected'to the die only when needed.-

In any event, the'handle allows the operator to place the mandrel and die in position eventhough the opening in the plate is substantially'- removed from the operator and-relatively inaccessible and thus access to diierent points interiorly of an ,airplane cover, for example, may easily be had. Since it is only necessary .to insert the mandrel through the opening in the plate, and lightly hold the mandrel in place while the mechanism is pushed over the end of the latter, it can be easily seen that an operator will have no difficulty in performing the work neces? iluld pressure may automatically be supplied to perform the dimpling operation. In this system,

when the pressure on the piston reaches a predetermined vamount in the dimpling operation. au-

tomatic reversal of fluid flow vmay occur so that the piston will be reversed automatically.

. In all thesystems, it is desired that the control be simple and handy for the operator, such as by employing a trigger on the handle of the gun and that the lines I9 and 44 be flexible in character so that the fluid supplying or developing source can be located remotely to the dimpling mechanism from which it follows that the operator may be at some distance from the source of iiuid pressure while still maintaining complete control sary at the die side of the structure. Since after the dimpling operation the mandrel is definitely released from the mechanism, all the operator needs to do is to pull the mandrel away from the sheets of metal.

Dimpling can be rapidly performed in this manner even at points inaccessible and all dimpling operations can be performed while the sheets are in place on airplane wings or iuselages or other installations where sheets may be dimpled for subsequent riveting. Aside from this,

the mechanism can be adjusted so that bending of the sheets that ordinarily would occur as a Y l result'of dimpling can be neutralized or counteracted so that iinally undesirable deformations or bends 6.811 be avoided in the sheets. By having the mechanism connected to a remote source of fluid under pressure,"the operator can quickly move lfrom point' to point for eiecting one dimpling operation after another and since the gun is compact and light,` thiseprocedure is not -fatiguing Moreover, since the entire operation can be controlled by means of a trigger on the handle, all that the operator needs to do is to move the gun from one-place to another and push it over the mandrel or mandrels successively and repeatedly move the trigger for effecting the dimpling operations. Two operators, one handling the mandrel and die device and moving it from point to point, and the other operating the dimpling mechanism and moving it from point to point, thus can rapidly eiIect one dimpling operation afteranother wlule the sheets It may be added gripping means, a die member to the other side of the sheets and having .a pm adapted to project through said opemng-m the are in place on the structure. Rapidity of dimpling of airplane structures is thus increased and the dlmpling operations are performed accurately and uniformly.

Although one form of the invention has been illustrated and described in detail, it will be apparent to those modifications may be made without departing from the scope of the appended claims.

What is claimed is: l

1. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a lpin may be pushed through the tool and engaged by the pin gripping means, a die member to be disposed at the other side of the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, an axially movable member on the casing and extending along the tool, means on the end of the member adapted to contact the sheet skilled in the art that various Y metal around the dimpling area in order to modil fy bending of the sheets during the dimpling operation, retractable guide means on the member and disposed adjacent the fruSto-conical c nd of the tool when the latter is in inoperatwe position so as to guide the pin into the bore, means normally urging the member outwardly along the tool axis and a. stop for limiting such axially outward movement of the member so that the guide means may be disposed in operative position when the tool is moved to its inoperative position, said means on the end of the member for contacting the sheet metal comprising a resilient rubber bushing, and an annular washer of relatively hard material providing an end face portion on the outer end of the bushing.

2. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting ing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin be disposed at latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and 'for returning the gripping means and tool to inoperative positions, an axially movable member on the casing and extending along the tool, means on the end of the member adapted to contact the sheet metal around the dimpling area. in order to modify bending of the sheets during the dimpling operation, retractable guide means on the member and disposedadjacent the frusta-conical end of the tool when the latter is in inoperative position so as to guide the pin into the bore, means normally urging the member outfrom one end of the casl wardly along the tool axis and stop for limiting such axially outward movement of the member so that the guide means may be disposed ln operative position when the tool is moved to its inoperative position, said means on the end of the member for contacting the sheet metal comprising \\a resilient rubber bushing and an annular relatively hard washer of angular 'cross section fitting the inner peripheral edge of the outer end of the bushing and providing a relatively rigid end face portion for contacting the sheet metal immediately adjacent the dimpling area.

3. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with' the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to be dis-posed at the other side of the sheets and having a pin adapted to project th'rough said opening in 'the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, an axially movable tubular member on the casinar and through which th'e tool extends, and a resilient rubber bushing fastened on the outer end of the axially movable member and including an annular washer oi relatively hard material on the end of the bushing and forming a part thereof.

4. An apparatus for forming a dimple around an opening in metal sheets comprising a. tubular casing. pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shapedend adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed-through the tool and engaged by the pin gripping means, a die member to be disposed at the other side of ,the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling I positions and for returning the gripping means and tool to inoperative positions, an axially movable tubular member on the casing and through which the tool extends, and a resilient rubber bushing fastened on the outer end of the axially movable member and including an annular washer of relatively hard material oh the end of the bushing and forming a part thereof, said washer being angular in cross section and having an annular flange extending radially outwardly and an axial or cylindrical flange extending within the opening in the bushing.

5. An apparatusfor forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to be disposed at the other side of the sheets and having a pin adapted to project through said opening in the latter and through saidbore for engagement with said gripping means, means for relatively moving the gripping means and tool axially .oi' the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping. means and tool to inoperative positions, an axially movable tubular member on the casing and through which tbe tool extends,A retractible-guide means on the member and disposed adjacent the frusto-conical end oi the tool when the latter is in inoperative position so as to guide the pin into the bore, resilient means on the outer end of the tubular member for engag- Ving the sheet metal around the area to be dimpin may be pushed through the tool and engaged by the pin gripping means, a die member to berdisposed at the other side of the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relativelv moving the gripping means and tool axially oi' the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping Imeans and tool to inoperative positions, an axially movable tubular member on the casing and through which the tool extends, retractible guide means on the member and disposed adlacent the frusta-conical end of the tool when the latter is in inoperative position so as to guide the pin into the bore, means on the end of the tubular member for engaging the sheet metal around the area-to be dimpled so as to side, said tool having acentral bore and being aligned with the pingripping means so that a pin may be pushed through the tool and engaged by the pin gripping means. a die member toY be disposed at-the other side of the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means land tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions. an axially movable tubular member on the casing and through which the tool extends, retractible -guide means on the member and disposed adjacent the frusta-conical end of the tool when the latter is in inoperative position so as to guide the pin into the bore, means on the end of the tubular member for engaging the sheet metal around tlfe area to be dimpled so as to modify bending of the metal around the area to be dimpled, and means on the casing for eecting axial movement of the member including the guide means thereonduring the dimpling of the metal so as to apply pressure to the sheet metal around the area being dimpled, said means for' eiecting axial movement of the member being adjustable so as to enable varying the pressure applied to the sheet.

8. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from onefend oi' the 0, disposed at the other side oi' the sheets and havmodify bending of the metal around the area to be dimpled, and means on the casing for eflecting a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, an axially movable tubular member on the casing and having an end wall through which the tool extends, retractible guide means in said end w for guiding the pin into the bore, and a resilient element fastened directly to the outer end i'ace ofsaid end wall for engaging the sheet metal around the area to be dimpied so as to modify bending oi' the' metal around the area to be dimpled.

LOUIS (2. HUCK. 

